The present invention relates to a method and an arrangement to provide a connection to a wireless terminal device depending on a location thereof such that, for the connection setup, a network computer is automatically contacted in whose wireless communication range the wireless terminal device currently resides, even if the connection code of another network computer has been entered by a communication subscriber that desires a connection to this wireless terminal device.
In recent years, wireless devices such as DECT telephones have gained ever wider acceptance in private networks. The DECT standard (Digital Enhanced Wireless Telephone) merely standardizes the air interfaces between a base station (Radio Fixed Part) and terminal device (portable part). Due to the often limited transmission power of wireless devices, their range of mobility is limited to the transmitting and receiving range of a respective base station. To expand the radius of activity of mobile devices of this type requires a number of base stations, whose wireless communication ranges mutually overlap or at least adjoin one another. To cover very large surface areas for the wireless communication, such as are represented by expanded industrial parks or cities, it is frequently necessary to provide base stations at a variety of network computers, in order to have available a sufficiently large wireless communication range for applications of this kind. The system structure of communication arrangements such as this and the communication methods used must guarantee that, given the moving of a wireless terminal device through the various wireless communication areas, it is assured that problems involving the stability of the connection do not arise in the wireless communication in the transition between these communication areas. This wandering thorough different wireless communication areas is known as roaming in the professional jargon. In particular, given roaming of this kind, it must be guaranteed that a wireless terminal device which is normally reachable via a communication code in the form of a telephone number, which switches a connection through to this device via a specific network computer, is also reachable if it is located in the wireless communication region of the base station of another network computer which can be reached via a different telephone number. This problem is solved in a communication system of the HICOM 300 type, currently marketed by Siemens AG, by a specific assembly that is present in each network computer. This assembly guarantees by network-wide communication that a wireless terminal device can roam arbitrarily.
But it is desirable in the sense of a universal usability of network computers to store functions other than pure switching functions externally to the computer and to establish auxiliary functions in the sense of a client-server concept.
An object of the present invention is to provide a method and an arrangement which combine the usability of optimally universal network computers, which execute pure switching functions only, with the required functions for the wide-area roaming of wireless terminal devices.
This object is achieved in accordance with the invention in a method wherein it is determined, via a mobility server having wireless connection information about a first wireless terminal device, having a first communication code for enabling a communication connection to a first network computer, whether the first wireless terminal device is located in a first wireless communication area of the first network computer. A wireless connection of said first wireless terminal device is set up to the first network computer upon determining that the first wireless terminal device is located in the first wireless communication area. A wireless connection of the first wireless terminal device is set up to the first network computer via a second network computer, having a second wireless communication area within which the first wireless-terminal device is located, using the wireless connection information, upon determining the first wireless terminal device not being located in the said first wireless communication area.
In an embodiment of the inventive method, wireless connection information for a wireless terminal device is advantageously held ready in a mobility server, and a connection to the wireless terminal device is produced by means of this wireless connection information. In this way, it is possible to use universal network computers, and the wireless terminal device can still be reached via that computer in whose wireless communication region it is located, even if a communication subscriber who wishes to establish the connection to this wireless terminal device dials the number of a different network computer.
In an embodiment of the inventive method, the mobility server advantageously controls the setup of the wireless connection by means of the connection information, because it is possible in this way to use standard interfaces for the influencing of the switching process on the network computer, and because the technical outlay for implementing the method is kept low.
In an embodiment of the inventive method, an item of identification information is delivered by the wireless terminal device, which can be received by a base station at a respective network computer. In this way it can be guaranteed that a connection message can be generated by simple means, via which connection message the network computer via whose communication code this wireless terminal device can usually be reached learns the connection path via which a connection to the wireless terminal device can be currently set up.
In an embodiment of the inventive method, the wireless connection information in the mobility server is advantageously updated with the aid of the connection message that has been forwarded by one network computer to another network computer. This guarantees, in a technically and constructionally simple manner, the constant reachability of the wireless terminal device, regardless of its location.
In an embodiment of the inventive method, performance features of the respective wireless terminal device are advantageously loaded in a performance feature server, which controls the network computer depending on activated performance features. This enables use of standardized interfaces to control network computers. Further, the outlay for implementing the displaying of performance features on wireless terminal devices remains low, wherein it is possible at the same time to use universal network computers which execute switching functions only.
In an embodiment of the inventive method, a check is advantageously made, prior to the setup of a connection to the wireless terminal device, as to whether a performance feature has been activated which renders the connection setup to this wireless terminal device superfluous, such as call forwarding to a secretary or the activation of a mailbox (which can be realized in the respective home network computer). The connection request and the communication line which transmits this connection request arrive thereat. On the one hand, this prevents the network load from increasing due to the setup of unneeded connections, and on the other hand, it guarantees a high flexibility with reference to the use of a wide variety of performance features.
In an embodiment of the inventive method, different network computers whose wireless communication areas border one another are advantageously combined into a group. In this way unrestricted movement of the wireless terminal equipment within the wireless communication areas of these network computers is possible. The method also guarantees that the wireless terminal device can be reached at all times. This method also enables the establishment of private and public wireless communication areas of arbitrary size.
In an embodiment, an arrangement comprising at least two network computers that are connected to each other; a mobility server, which is connected to a network computer, contains connection information to a wireless terminal device; and a wireless terminal device. This arrangement represents the minimal configuration with which the object of the invention is achieved and with which the ability to reach the wireless terminal device via the setup of a connection by means of the mobility server is guaranteed. This arrangement is attractive, because it solves the problem of the invention using technically simple means.
In an embodiment of the inventive arrangement, means are provided for delivering identity information and for receiving such information as delivered by the wireless terminal device, from which information, in connection with connection information of the respective network computer, additional means generate a connection message, which can be forwarded to other network computers and which guarantees the reachability of the wireless terminal device. This arrangement and these means easily guarantee the reachability of the wireless terminal device within a wide variety of wireless communication areas of different network computers, via a single communication code of a home network computer of this wireless terminal device.
In an embodiment of the inventive arrangement, there is a performance feature server, which makes available a wide variety of performance features for the wireless terminal device and which controls the network computer depending on these performance features. In this way, it is possible to use network computers which only have switching functions, and at the same time to realize and display a wide variety of performance features for the wireless terminal devices, thereby making available a highly flexible universally usable communication arrangement.